Automatic control of toner concentrations

ABSTRACT

Controls for manually selecting toner concentrations in a xerographic imaging system are overridden to prevent overtoning. A drive mechanism responsive to copy production incrementally resets the toner controls to a standard toner concentration when that level is exceeded.

United States Patent Turner [4 1 Sept. 19, 1972 AUTOMATIC CONTROL OFTONER CONCENTRATIONS Lyman H. Turner, Pittsford, NY.

Stamford,

Inventor:

Xerox Conn.

Filed: Dec. 23, 1971 Appl. No.: 211,380

Assignee: Corporation,

Us. 01. ..3ss/3, 1 17/175, 118/637, 222/199 Int Cl. ..G03g 15/08 FieldofSearch....355/3; 118/637; 117/16, 17.5;

[56] References Cited UNITED STATES PATENTS 3,348,522 10/1967 Donohue..1l8/637 X 3,348,523 10/1967 Davidson et a1. ..1 18/637 X 3,376,8544/1968 Kamola ..1 17/ 17.5 X

Primary Examiner-Robert P. Greiner Attorney-James J. Ralabate et a1.

[57] ABSTRACT Controls for manually selecting toner concentrations in axerographic imaging system are overridden to prevent overtoning. A drivemechanism responsive to copy production incrementally resets the tonercontrols to a standard toner concentration when that level is exceeded.

17 Claims, 6 Drawing Figures PATENT EDSEP 19 m2 SHEET 1 [IF 4 PATENTEDSE? 19 I972 SHEET 2 [IF 4 AUTOMATIC CONTROL OF TONER CONCENTRATIONSBACKGROUND OF THE INVENTION This invention relates to the dispensing ofxero' graphic toner particles. More specifically, this invention relatesto novel methods and apparatus for limiting the dispensing rate of apowder from a hopper having a reciprocating dispensing gate.

Reciprocating gate dispensing apparatus is disclosed in U.S. Pat. No.3,013,703 to Hunt, the disclosure of which is incorporated herein byreference. The dispensing apparatus includes a hopper for holding apowder, e.g., xerographic toner particles, with a dispensing plateslightly spaced from an orifice in the bottom of the hopper. In thespace is located a reciprocating device or metering element thatcontrols the flow of powder through the gaps or gate formed between thehopper orifice and the dispensing plate. The flow rate of powder iscontrollable by changing the length of travel of the reciprocatingdevice and the reciprocating frequency, the number of cycles per unittime the device is reciprocated.

In many xerographic machines it is the practice to tie the reciprocatingfrequency to the rate of toner image production to add toner to axerographic development system at a rate related to toner consumption.Thereafter, the quantity of powder being dispensed can be scaled up ordown by increasing the length over which the reciprocating devicetravels. This scaling operation is commonly performed by an operatoraction such as pushing a button or moving a handle to one ofa pluralityof toner settings.

A problem can arise in the foregoing xerographic systems if the operatorfails to properly scale the toner concentration levels to suit thecopying requirement of the machine. When a different type of copy isdesired, e.g., when a machine making line copies is used to produce copyhaving solid area coverage, the operator temporarily scales the tonerconcentration for that particular task. Should the operator fail toreturn the concentration to the line copy level, it is reasonable toexpect trouble somewhere in the system due to excess toner quantities.

Accordingly, it is a primary object of this invention to devise methodsand apparatus for automatically changing toner concentrations inxerographic systems.

More specifically, it is an object of the invention to changeautomatically toner concentration in a xerographic system over a finitenumber of copy forming cycles.

It is also an object of the present invention to eliminate human errorsin determining toner concentrations for xerographic copying systems.

Another object of the present invention is to regulate the length oftravel of the reciprocating device in a powder dispenser of the typedisclosed in the Hunt Patent.

Yet a further object of this invention is to devise a drive mechanismcapable of imparting incremental angular displacements totaling lessthan 360 of rotation to a drive member in response to multiple 360rotations of a driving member. This object is, of course, directed tothe solution of the other objects.

These and other objects of the instant invention are realized bycoupling a drive mechanism to the operator control device for scalingpowder concentrations. The drive mechanism in question is responsive tothe number of copies produced, or other production criteria, and acts onthe operator control device. In the specific xerographic embodimentdisclosed herein, the drive mechanism automatically resets byincremental amounts during the production of a fixed number of copies anoperator control handle to a standard position when the tonerconcentration level represented by the standard position is exceeded.Undertoning, i.e., toner concentrations associated with a handle settingbelow the standard level, does not harm the system and is usuallyreadily detected in the quality of the copy. On the other hand,overtoning, i.e., too great toner concentrations, may not affect copyquality directly and go undetected until a system failure occurs.

DESCRIPTION OF THE DRAWINGS Other objects and features of the presentinvention will be apparent from the present description and from thedrawings which are:

FIG. 1 is a side elevation, partly in section of a xerographic systemusing a reciprocating gate toner dispenser having an operator actuatedhandle for scaling toner concentrations.

FIG. 2 is a view of a reciprocating gate powder dispenser, an operatorcontrolled handle for varying the length of travel of the reciprocatingdevice and the drive mechanism of the instant invention.

FIG. 3 is a side elevation view of the operator handle and drivemechanism in FIG. 2.

FIG. 4 is a perspective view of the reciprocating gate dispenser shownin FIG. 2.

FIGS. 5 and 6 are enlarged sectional views of two embodiments of drivemechanisms according to the instant invention.

DETAILED DESCRIPTION The transfer xerographic system of FIG. 1 has thedrum 1 which includes a photoconductive layer coated onto anelectrically grounded metal cylinder. The drum as described defines acontinuous, reusable xerographic plate or member. The drum is journaledin a frame to rotate in the direction indicated by the arrow to causethe free or image forming surface of the drum to sequentially pass aplurality of xerographic processing stations.

The charging station A includes the corotron 2. Corotron 2, e.g., thatdescribed in U.S. Pat. No. 2,836,725, is coupled to an appropriateelectrical potential and positioned relative to the drum to depositcharge on the free surface of the drum so as to elevate the free surfaceto a substantially uniform electrical potential, e.g., 800 volts.

The exposure station B includes appropriate lamps 3 and lens 4 mountedto cooperate for a line-by-line scan of an original placed face down oncopyboard or platen 5. The light image created by the scanning of anoriginal is projected onto the free surface of drum 1 through theaperture 6 in the light stop 7. The electrical potential of the drumdrops substantially in the areas of the xerographic plate absorbing theincident light. The areas absorbing the light, in the present positiveto positive copying system are referred to herein as the backgroundareas. An example of a background potential is 200 volts when the drumis charged as in the earlier example of 800 volts. The areas of lowerpotential actually may comprise the image area in a negative to positivecopying system. This latter copying system is not discussed in detail toavoid redundancy because the present description applies except forlogically necessitated changes.

Adjacent the exposure station is the development station C whichcontains the toner particles for making the latent electrostatic imagevisible. FIG. 1 shows a cascade development system, by way of example,which includes a motor driven bucket-type conveyor 10. The developermaterial 11 includes carrier particles and toner particles and is storedin a sump in the bottom of the housing 11. The buckets scoop up thedeveloper and carry it to the upper portion of the housing where thedeveloper is poured or cascaded over the hopper chute onto the drum 1.

As the developer cascades over the free surface of the drum, the tonerparticles adhere to the latent electrostatic image because of theelectric fields associated with the latent image. The toner iselectrostatically charged triboelectrically due to a mixing action withthe carrier particles. Toner particles consumed during the developmentprocess is replenished by a toner dispenser 13 mounted within housing11.

The pre-transfer station D includes the pre-transfer corotron 15 andpre-transfer lamp 16. Station D conditions the xerographic plate andtoner thereon such that only image area toner particles are transferredto a transfer member 17 at station E. The pre-transfer corotron 15operation is disclosed in US. Pat. No. 3,444,369 to Malinaric.

The transfer station includes, by way of example, means for feeding atransfer member 17 in registration with the toner image on the drum andthe transfer corotron 18 which charges the backside or non-imagecarrying side of a transfer member to a high potential, e.g., +2,000volts for the earlier given examples of +800 and +200 volts at the freesurface of drum 1. The electric field established by the chargedeposited by corotron l8 and the potentials associated with the drumcause the toner particles in image areas to transfer to member 17.

The transferred toner image is permanently fixed to member 17 at thefixing station F. Station F includes, by way of example, electricalheating elements 21 that heat soften the toner particles to bond them tothe transfer member.

The cleaning station G includes a cleaning corotron 22 and the rotatingbrush 23 positioned within vacuum housing 24. Corotron 22 is coupled toan alternating potential source to neutralize any non-transferred toner,that is charge the remaining toner to a new ground potential when thedrum is grounded. The brush sweeps up the remaining particles while thevacuum drawn on the housing 24 pulls the toner into a filter located inbox 25.

The cleaning station also includes a lamp 26 for flooding the freesurface of the drum with light. Thereafter, the drum once again passesstation A and the next cycle begins.

The development station C also includes a background electrode 30positioned inside housing 12 spaced about a half inch from the drum attheir closest points. Electrode 30 is electrically biased because it isrelatively greatly spaced from the latent image on the drum and becausethe bias is properly selected, it does not act like a developmentelectrode as taught in Carlson US. Pat. No. 3,147,147. Electrode 30 isbiased so as to suppress toner powder clouds which means that fewertoner particles adhere to the drum in the background areas in the firstinstance. (See for example Robinson US. Pat. No. 3,412,710 and Aser etal. U.S. Pat. No. 3,424,13l). The electrode 30 includes conductivesurface facing the drum which is coupled to the high electricalpotential. The electrode also includes insulating means to electricallyinsulate the conductive surface from the housing 12.

Attention is now directed to the reciprocating gate dispenser 13 shownin FIGS. 2 and 4. The dispenser includes a hopper or container 33.Although the hopper or container 33 may be made of any suitable materialin any size or shape, the hopper shown is fabricated from sheet metalinto a rectangular open-ended box having vertical side walls 34 and endwalls 35, the upper ends of the walls being bent outward to formhorizontal flanges by means of which the hopper may be attached to asuitable support.

At opposite ends of the hopper are positioned depending bearing blocksor support members 36 and 37 for supporting the remaining elements ofthe toner dispenser with the bearing blocks or support members beingattached to end walls.

The bottom of the hopper is partially closed by a dispensing plate orplatform 40 positioned in spaced vertical relation below the lower edgesof the walls of the hopper. The dispensing plate or platform 40 which isas wide as the hopper, is secured to the underside stepped portions ofsupport members 36 and 37. The dispensing plate or platform 40 combineswith the walls of the hopper to provide a reservoir having narrowelongated discharge outlets, discharge passages or gates 41 for the flowof toner particles.

To effect substantially uniform flow of toner particles through theoutlets or passages 41 there is provided a metering element, generallydesignated 42, having a dispensing grid 43 positioned for reciprocatingmotion in the space between the dispensing platform and the lower edgesof the walls of the hopper. The metering element 42 has the dispensinggrid formed by a top wall having a series of transverse perforations orslots formed therein, and depending side walls 44. For ease and economyin manufacturing the metering element is formed as a sheet metalstamping, the slots being formed relatively close to each other and tothe transverse edges of the top wall so that after the slots were formedthere remains only narrow strips of metal simulating wires 45, the widthof the metal remaining between slots being only sufficiently wide toprevent them from being bent out of shape in the stamping process.

The metering element 42 is supported by parallel guide rods or rodmembers 47 extending through holes in plates 48, the ends of the rodmembers being journaled for reciprocating motion in apertures 49 formedin bearing blocks 36 and 37. The movement of rod members 47 to the leftis limited by collars 50 ad justably secured thereto by set screws whilemovement of the metering element 42 with respect to rod members isprevented by collars secured to the guide rods inboard of the supportplates 48.

For effecting movement of the metering element a plunger rod 52 isjournaled in third aperture 53 in the bearing block, to be actuated by asuitable power source such as cam 54 to effect the forward stroke of themetering element to the right. To limit the movement of the plunger rod,retaining rings are secured in suitable grooves at each end of theplunger rod. The return stroke of the metering element is effected bycoiled springs 55 encircling the rods 47 and abutting at opposite endsagainst the bearing block and a support plate 48 to bias the meteringelement to the left.

As shown, the dispensing grid 43 is positioned between dispensingplatform 40 and the lower edge of the walls of the hopper in spacedrelation to each other to permit free reciprocating movement of thegrid. The space or clearance between each of thelast-named elements maybe varied during fabrication to accommodate the particle size of toneror other granular material to be dispensed. For example, it has beenfound that a very satisfactory uniform dispensing rate for toner havinga particle size of from 0.7 to 0.9 microns can be had by a tonerdispenser in which the spacing between the dispensing platform and thelower edges of the walls of the hopper is between 0.28 to 0.038 inch,preferably 0.033 inch, while the spacing between both the dispensingplatform and the dispensing grid and the low edges of the walls of thehopper is between 0.007 to 0.010 inch, preferably 0.0075 inch when using0.018 inch thick sheet metal for the dispensing grid.

In the operation of the toner dispenser, a supply of toner particles isplaced within the hopper, the hopper and dispensing platform forming areservoir for the toner particles. Upon reciprocating of the dispensinggrid 43 toner particles fall onto the dispensing platform and are pushedforward by the individual wires 45. As the toner particles arepushedforward, either on the forward stroke or on the return stroke, they takethe path of least resistance and gravitate toward the outer margins ofthe wires, falling through the open grid work of the dispensing grid andover the edge of the dispensing platform.

The element 42 is shown sufficiently shorter than the length of thehopper so that the collars can be adjusted on rod members 47 to preventthe dispensing grid from striking support members 36 and 37 as it isreciprocated, the length of stroke also being adjusted so that the pathof movement of a wire overlaps the path of movement of the next adjacentwire.

In the embodiment of the toner dispenser shown, the respective spacingbetween the dispensing platform, the dispensing element or grid and thelower edges of the hopper walls is fixed. Accordingly, the dispenserprovides a uniform dispensing rate per stroke or cycle. Therefore, thedispensing rate may be changed by vary ing the dispensing frequency,i.e., the number of strokes or cycles per unit time, or by varying thelength of stroke of the dispensing element 42.

In the environment of the xerographic system of FIG. 1, the dispensingfrequency is directly proportional to the number of revolutions per unittime of drum 1. This means that the dispensing frequency is directlyproportional to the number of copies formed on transfer sheets 17 perunit time. As mentioned at the outset, this described system provides adispensing rate for toner which is, of course, related to the number ofcopies generated. The proportionality is provided simply by mechanicallycoupling the cam 54 to the shaft of drum 1. The dispensing frequency isfixed for the system of FIG. 1 and toner concentrations are scaled upand down by varying the length of travel of dispensing grid 42. This isdone by varying the position of the abutment plate 56 relative to theplunger rod 52. The location of plate 56 determines how far the plungerrod can travel to the left. In FIG. 2, the plate is shown located at itsleft-most position which defines the maximum stroke length. The dashedlines 57 in FIG. 2 indicate the rightmost position of the plate 56.

The abutment plate has shaft 58 coupled normal to the plane of the plateand slidably mounted by a bearing 59 in frame plate 60. Shaft 58 iseffectively an extension of the plunger rod 52 in that shaft 58 isreciprocated as cam 54 is rotated about drive shaft 61. The drive shaft61 is in turn appropriately coupled by belt 62 and pulley 63 forrotation at an angular rate proportional to the rotation of drum 1. Infact, the belt 62 is coupled to a pulley mounted on the shaft of drum 1.Abutment plate 56 is positioned at a location at or between the rightand left most positions by the operator controlled handle 64.

Handle 64, in the embodiment of FIGS. 1,3 and 5, is

journaled for rotation in a frame plate 67. The pivotally mounted lever68 is coupled to the handle by the spring 69. A rigid wire cable 70 isfixedly coupled to lever 68 at one end and fixedly coupled to abutmentplate 56 at its opposite end. The cable is passed through the tubing orconduit 70 which in turn is fixedly coupled to the frame plates 60 and67 Pivotal movement of handle 64 is translated into linear displacementof abutment plate 56 by the cable, spring and lever connecting the two.Accordingly, the length of travel of the dispensing or metering element42 is set by operator adjustment of handle 64.

The novel drive mechanisms of the instant invention reset the handle 64to a standard position when the handle is located by an operator to aposition causing a toner dispensing rate greater than that establishedby the standard handle position. Each drive mechanism includes a one-wayclutch coupled at its output side to handle 64, a yoke member 73 coupledto the input side of the clutch, cam peg 74 fixedly coupled to pulley 63which is in turn mounted on the drive shaft 61 rotating thereciprocating cam 54 and the stop plate 75 fixedly coupled to the frameplate 67.

The present drive mechanisms are able to impart in equal increments atotal angular displacement of less than 360, normally around 20 to 30,to the handle in response to continuous rotation of the pulley 63. Theyoke 72 and the cam peg 73 tap the continuous rotation of pulley 63 andsupply the energy to handle 64 through a one-way clutch. The forkportion 78 of the yoke straddles drive shaft 61 and peg 73. The peg is acam and the fork is its follower and they act together to impart a backand forth wrench motion to the body 79 of the yoke. The toner settingrepresented by the angular position of handle 64 is changed by somedesired incremental amount during each wrench cycle of the yoke. Thechange to the toner setting can occur during either the clockwise orcounterclockwise rotation of the yoke at the discretion of the designer.One wrench cycle is obtained per one revolution of pulley 63 but thismay be scaled up or down.

The object is to remove handle 64 back to the stop pad 75 within a fixednumber of revolutions of pulley 63. The location at which the handleabuts pad 75 is selected as the standard handle position definedearlier. Any position of the handle to the right of pad 75 (FIG. 3)yields undesirably high toner dispensing rates as described. Lower tonersettings, i.e., settings to the left of pad 75 (FIG. 3), are obtained bymoving the location of the stop pad.

The present drive mechanism allows a zero toner dispensing rate. Thezero rate is obtained when the handle positions the abutment plate 56 tothe rightmost location 57. The shaft 58 is out-of-contact with cam 54when the abutment plate is at position 57. Consequently, no toner isdispensed at this handle setting. A zero rate may be desirable when aplurality of copies are being made that consume only a small quantity oftoner. For example, a zero setting may be desired when the copiesinclude only a one sentence message. The operation of the embodiments ofthe present drive mechanism may be understood by reference to FIGS.

and 6.

The embodiment of FIG. 5 includes the stop pad 75 and the wrap springclutch 80 having its input hub 81 fixedly coupled to the common shaft 82by a set screw 83 and its output hub 84 freely rotatable about shaft 82and fixedly coupled to lever 68 (best seen in FIG. 3). Lever 68 iscoupled to the handle 64 by the coil spring 69. The embodiment of FIG. 5also includes the yoke member 73 fixedly coupled to the common shaft 82by means of a set screw 87 in the cap 88 fixedly coupled to the yoke.The handle 64 is journaled for rotation about the threaded barrel 89which is fixedly coupled to the frame plate 67 by the nut and washer 90and 91.

The back and forth wrench motion of the yoke described earlier rotatesthe input hub 81 of the clutch back and forth. The cylindrical coilspring 94 is loosely fitted over the input 81 and output 84 hubs withtang 95 extending upward free of the clutch housing. When input hub 81is rotated clockwise, for example, the diameter of the cylindrical coilspring contracts thereby frictionally coupling the two hubs together.Consequently, the output hub and lever 85 follow the rotation of yoke73. When input hub 81 is rotated counterclockwise, for example, the coilspring is uneffected and the output hub and lever 68 do not follow therotation of yoke 73.

The handle 64 is incrementally rotated back to the stop pad 75 as aresult of the foregoing operation. With the handle restrained by thestop pad, the tripper bar 96 fixedly coupled to handle 64 engages tang95 and prevents the coil spring from wrapping around the two hubs duringthe clockwise portion of the wrench cycle of the yoke. Therefore, theoutput hub 84, and lever 68 do not follow the movement of yoke 73 ineither the clockwise or counterclockwise directions while the handle isat the stop pad.

To position the handle against a limit or zero dispensing rate stop,handle 64 is pulled to the left (FIG. 5) to clear the stop pad 75. If itis not positioned against the limit stop, the drive mechanism will movethe handle to that position in a time proportional to a multiple ofanumber of drum revolutions.

The embodiment of FIG. 6 includes the stop pad and the one-way rollerclutch 101 having its input hub 102 fixedly coupled, e.g., welded, tothe yoke 73. The hub 102 includes asymmetrical cavities 103 in which theroller bearings 104 are seated. The hub rotates freely about commonshaft 105 when yoke 73 is rotated clockwise, for example, and is lockedto shaft 105 when yoke 73 is rotated counterclockwise.

Fixedly coupled to the other end of common shaft 105 is the frictionslip clutch 106. Clutch 106 includes the first and second hubs 107 and108 having friction layers 109 and 110 of cork or other high frictionmaterial facing each other. The handle 64 is journaled for rotationabout the common shaft 105 between the cork surfaces 109 and 110. Thefrictional forces exerted by the surface of layers 109 and 110 on thehandle are controlled by means of the leaf spring 111. The screw 112 isthreaded to mate with threads in the hub 107 and has the leaf springbetween it and the hub to vary spring tension when the screw is turnedin and out of the threaded hub. The tension in the leaf spring isadjusted by means of screw 112 to enable the friction layers 109 and 110to rotate handle 64 when the common shaft 105 is rotated. Shaft 105 isrotated on the clockwise, for example, portion of the wrench cycle ofyoke 73 as explained earlier.

The handle is angularly displaced in increments by the friction clutch106 in the manner described until it engages the stop pad 75. Thefrictional forces between layers 109 and 110 and the handle are notsufficient to overcome the force exerted on the handle by the stop pad.The friction clutch simply slips or free wheels in this situation. Onceagain, pulling the handle to the left (FIG. 6) clears it of stop pad 75and the drive mechanism will pull the handle to a limit or zeroconcentration handle position. The cable 70 is fixedly coupled directlyto the handle 64 in this embodiment rather than by the spring 69 andlever 68 as in the embodiment of FIG. 0.028

The foregoing embodiments may be varied without departing from the scopeof the current invention. An example would be to adapt the embodimentsdescribed to a system wherein the operator control means is a pushbutton rather than a handle. The basic concept of incrementally steppingtoner concentration settings during multiples of a copy forming cycle,or other cycle in which a powder is consumed, may be readily adapted toother environments in light of the present teaching. Accordingly, suchmodifications are intended as part of this invention.

What is claimed is:

l. Electrostatic imaging apparatus comprising copying means for creatingelectrostatic latent images on plate members,

developing means positionable relative to a plate member for developinga latent image on the plate forming a toner particle image,

toner particle dispensing means for supplying toner particles to thedeveloping means for the formation of toner particle images,

operator control means coupled to the dispensing means for establishingthe quantity of toner particles supplied to the developing meansincluding a plurality of operator selectable toner settings each ofwhich make a different quantity of toner particles available to thedeveloping means and drive means coupled to the control means forchanging an operator selected toner setting in response to the number oftoner images formed.

2. The apparatus of claim 1 wherein said drive means includes means forincrementally changing said toner setting.

3. The apparatus of claim 1 wherein said drive means includes means forchanging an operated selected toner setting to a standard toner setting.

4. The apparatus of claim 1 wherein said plate member includes axerographic plate and said copying means includes means forelectrostatically charging the plate and means for exposing the plate tolight to create the latent image.

5. The apparatus of claim 4 wherein said xerographic plate is reusable.

6. The apparatus of claim 1 wherein said dispensing means includes areciprocating gate dispensing means.

7. The apparatus of claim 1 wherein said control means includes apivotally supported handle manually adjustable to the plurality of tonersettings.

8. The apparatus of claim 6 wherein said dispensing means includes areciprocating gate dispensing means and said control means includesmeans for varying the length of travel of a reciprocating member in saiddispensing means for sealing the quantity of particles supplied to thedeveloping means.

9. The apparatus of claim 8 wherein said control means includes apivotally mounted handle coupled to said dispensing means forestablishing a different length of travel for the reciprocating means atdifferent angular positions of the handle.

10. The apparatus of claim 1 wherein said control means includes acontrol shaft adjustable to a plurality of angular settings comprisingthe toner settings.

11. The apparatus of claim 10 wherein said drive means includes meansfor angularly displacing said control shaft by some incremental angularamount upon one revolution of a drive member shaft rotated in proportionto a cycle during which a toner image is formed.

12. The apparatus of claim 11 wherein said drive means includes a yokemember coupled at one end to a common shaft and at the other end to thedriving member to impart a wrench motion to the yoke member in responseto rotation of the driving member shaft and clutch means coupled betweensaid common and control shafts to rotate the control shaft in onedirection in response to the wrench motion of the yoke member.

13. The apparatus of claim 12 wherein said drive means further includesstop pad means for limiting the rotation of control shaft to an angularposition corresponding to a standard toner setting.

14. The apparatus of claim 12 wherein said clutch means includes rollerclutch means coupled between said yoke member and the common shaft andfriction clutch means coupled between the control and common shafts.

15. The apparatus of claim 12 wherein said clutch means includes wrapspring clutch means coupled between the common and control shafts.

1. Electrostatic imaging apparatus comprising copying means for creatingelectrostatic latent images on plate members, developing meanspositionable relative to a plate member for developing a latent image onthe plate forming a toner particle image, toner particle dispensingmeans for supplying toner particles to the developing means for theformation of toner particle images, operator control means coupled tothe dispensing means for establishing the quantity of toner particlessupplied to the developing means including a plurality of operatorselectable toner settings each of which make a different quantity oftoner particles available to the developing means and drive meanscoupled to the control means for changing an operator selected tonersetting in response to the number of toner images formed.
 2. Theapparatus of claim 1 wherein said drive means includes means forincrementally changing said toner setting.
 3. The apparatus of claim 1wherein said drive means includes means for changing an operatedselected toner setting to a standard toner setting.
 4. The apparatus ofclaim 1 wherein said plate member includes a xerographic plate and saidcopying means includes means for electrostaTically charging the plateand means for exposing the plate to light to create the latent image. 5.The apparatus of claim 4 wherein said xerographic plate is reusable. 6.The apparatus of claim 1 wherein said dispensing means includes areciprocating gate dispensing means.
 7. The apparatus of claim 1 whereinsaid control means includes a pivotally supported handle manuallyadjustable to the plurality of toner settings.
 8. The apparatus of claim6 wherein said dispensing means includes a reciprocating gate dispensingmeans and said control means includes means for varying the length oftravel of a reciprocating member in said dispensing means for scalingthe quantity of particles supplied to the developing means.
 9. Theapparatus of claim 8 wherein said control means includes a pivotallymounted handle coupled to said dispensing means for establishing adifferent length of travel for the reciprocating means at differentangular positions of the handle.
 10. The apparatus of claim 1 whereinsaid control means includes a control shaft adjustable to a plurality ofangular settings comprising the toner settings.
 11. The apparatus ofclaim 10 wherein said drive means includes means for angularlydisplacing said control shaft by some incremental angular amount uponone revolution of a drive member shaft rotated in proportion to a cycleduring which a toner image is formed.
 12. The apparatus of claim 11wherein said drive means includes a yoke member coupled at one end to acommon shaft and at the other end to the driving member to impart awrench motion to the yoke member in response to rotation of the drivingmember shaft and clutch means coupled between said common and controlshafts to rotate the control shaft in one direction in response to thewrench motion of the yoke member.
 13. The apparatus of claim 12 whereinsaid drive means further includes stop pad means for limiting therotation of control shaft to an angular position corresponding to astandard toner setting.
 14. The apparatus of claim 12 wherein saidclutch means includes roller clutch means coupled between said yokemember and the common shaft and friction clutch means coupled betweenthe control and common shafts.
 15. The apparatus of claim 12 whereinsaid clutch means includes wrap spring clutch means coupled between thecommon and control shafts.
 16. The apparatus of claim 11 wherein saidplate member is a continuous xerographic plate and said driving membershaft includes a shaft rotating at an angular velocity related to therecirculating rate of the xerographic plate.
 17. The apparatus of claim11 wherein said control shaft includes a handle coupled thereto forenabling an operator to manually rotate the control shaft to one of thetoner settings.